The present invention relates to an air conditioner, especially and air conditioner used for an automobile.
Japanese Patent 57-47829 shows a conventional air conditioner, wherein an evaporator is defrosted by a gas-phase refrigerant which is at a high temperature and under high pressure. When the evaporator is frosted, the gas-phase refrigerant discharged from a compressor is introduced into the evaporator so as to defrost the evaporator. The refrigerant that has flowed through the evaporator is returned to the compressor through an accumulator as in the gas-phase process.
A conventional air conditioner is equipped with a heater core through which a warmed engine coolant flows. As shown in FIG. 9, an internal-combustion engine 1 is connected to heater core 3a of heater unit 3 through an inlet conduit 2 and an outlet conduit 4 on which a valve 5 is provided. The heater core 301 is disposed downstream of an evaporator 14, whereby air introduced by a fan 28 flows through the evaporator 14 and then through the heater core 3a. An electric heater, a combustion heater or a heat pump is used as an auxiliary heat source while the heater core 301 is used as a main heat source.
The conventional air conditioner shown in Japanese Patent 57-47829 is designed to defrost the evaporator by use of hot refrigerant, not to increase the heating efficiency. The temperature of the engine coolant is not elevated rapidly right after the engine is started, so that a long time is required to radiate enough heat from the heater core.
The conventional air conditioner having the auxiliary heat source has further problems as follows. The electric heater consumes a lot of electric energy; the combustion heater has a safety hazard; and the heat pump is not operative in cold climates.